Current commercial transport airplanes, and indeed most aircraft built today, have onboard a large amount of electronic and computer equipment. For commercial transports, the space required for electronic and computer equipment tends to be substantial, and the total volume required is roughly the same regardless of aircraft size. As a result, and particularly in smaller aircraft, space is at a premium. More importantly, space at the forward end of the fuselage in the vicinity of the pilot station is quite valuable.
One section of premium space in the forward fuselage section which has been heretofore been largely unavailable for stowage of electronic equipment is the space under the cockpit floor. This space is normally occupied by the nose landing gear and by the aircraft directional controls. In most "tricycle gear" aircraft, there is no easy way to completely displace the nose gear from this premium forward space. However, it would be most desirable to reduce space requirements for directional controls and for the accompanying operating mechanisms, mechanical linkages, and cables for those controls and the aircraft's brakes.
Aircraft control is normally described in terms of a three axis system, using the terms pitch, roll, and yaw. Neutral pitch position is when the aircraft's longitudinal axis is in a horizontal position along the direction of flight, a change of pitch involves moving the aircraft nose up or down. Neutral roll position is when wings are in a level position, rolling the aircraft involves moving one wing higher and one wing lower relative to a horizontal axis. Neutral yaw position is a straight ahead orientation, changing yaw involves turning the nose left or right so that the aircraft's longitudinal axis forms an angle with respect to the line of flight. Yaw stability in aircraft is normally achieved by employing the combination of a fixed vertical stabilizer and a movable vertical control surface usually referred to as the "rudder." Rudder control input is normally achieved by pilot operated foot pedals which are also employed to operate the brakes of the aircraft and steer it on the ground. When an aircraft is taxing on the ground, the rudder pedals are operably connected to a steerable nose wheel or wheels, and pushing one or the other of the pedals forwardly causes the nose wheel(s) to turn to the left or the right. In addition, the pedals are mounted for rotation about movable transverse axes at the lower portions of the pedals. By rotating the toe portions of the pedals forwardly and downwardly about these lower axes of rotation, the brakes can be applied.
There are a wide variety of rudder and brake pedal mechanisms. Typically, though, the known systems require cables, pivot arms, levers, and bellcranks to be located beneath the floor of each pilot station; and an aircraft, regardless of its size, will most often have two of these stations. Therefore, the space occupied by the rudder and brake operating mechanisms in the forward part of an aircraft is considerable.
The usual arrangement is to have left and right pedals, each mounted on a pivot arm so that the pedals move in arcuate paths. The two pedals are generally so interconnected that, when one pedal is displaced forwardly, the other pedal moves rearwardly toward the pilot. The pedals are commonly connected to cable systems which: (a) extend from the forward cockpit area to the tail section and are connected to the control device actuators which move the rudder, and (b) similarly connect the pedals to the brake actuators.
One of the shortcomings of most prior art foot pedal assemblies is that, for the pedals to have the linear travel needed for the pilot to provide adequate control, the pedal pivot arms and their associated components have been positioned below the floor level of the cockpit. Not only does this occupy space in the aircraft which could be used advantageously for other functions, but it limits the extent to which the pilot's seat can be moved forward. Forward positioning is desirable since it normally provides the pilot with greater visibility.
Basic control systems for commercial aircraft have also employed hydraulic systems (particularly for brakes). Hydraulic systems have the same above-discussed disadvantages as cable systems in that the pilot-actuated controls are similar; and the lines of hydraulic systems follow generally the same routes and take up at least as much space as the cables of a cable-type system.
Also, computerized electronic control systems, also known as "fly-by-wire" systems, have been available for some time. These systems have typically been employed only in military type aircraft and, until recently, have not been adapted to large, commercial, subsonic transport aircraft. However, improved component reliability in fly-by-wire systems is leading aircraft manufacturers toward the possibility of more widespread use of such electronic, computerized flight control arrangements.
In most proposed fly-by-wire control arrangements, the typical, pilot-operated rudder and brake pedal controls remain unchanged vis-s-vis conventional cable or hydraulic control systems. However, instead of the pedal acting on a cable or a hydraulic actuator, in an aircraft utilizing a fly-by-wire control system, the movement of a rudder pedal actuates a transducer, sending an electronic signal to one or more main flight control computers. The flight control computer in turn sends an electronic signal through an electrical lead to an actuator (typically hydraulic) in the vicinity of the control surfaces, brakes, steerable nose wheel, etc. The actuator moves the aircraft control surfaces to an extent commensurate with the pilot's manipulation of the control input devices or similarly applies the brakes or turns the steerable nose wheel of the aircraft.
Fly-by-wire type aircraft control systems have fewer interrelated mechanical linkages, and less space is needed for equipment. However, full advantage has not been taken of the possibilities offered by these systems.
In particular, one problem which has been until recently been ignored because of the limitations imposed by hydraulic and cable type systems and because the human engineering data we have today was not available when those systems were developed is that of providing ergometrically correct adjustment for the neutral position of control pedals to accommodate pilots of differing physical dimensions. For many years, the only adjustments provided allowed one to raise or lower the pilot seat and move it forward or backward to position a pilot at a comfortable location. Even in most of those few devices that did allow the neutral position of pedals to be adjusted, the adjustment has been along an operating path which was not optimum when considering human limb length and human limb rotation. Also, conventional systems for adjusting pilot seating and control mechanisms do not take into account both pilot comfort and the airline's requirement that each pilot position his or her eyes at a common "eye reference point" for a particular aircraft, regardless of pilot size.
A number of previously issued patents disclose foot-operated pedals for aircraft rudder, brake, or landing gear steering controls, and such devices are commonly used in present day aircraft. Specific patents which appear to deal with the problem of adjusting foot-operated, aircraft control pedals are discussed below.
U.S. Pat. No. 2,585,688 issued to Saulnier on Feb. 12, 1952, discloses a rudder pedal control system ultimately supported by a stationary base. Saulnier does not completely avoid the need for floor penetrations.
U.S. Pat. No. 2,478,546 issued to Pickens on Aug. 9, 1949, discloses an adjusting mechanism for rudder pedals. Although the rudder pedal itself is supported from above, the adjusting mechanism is independently supported by a forward bulkhead which leads to complexity and non-optimum use of available space. Further, the adjusting mechanism is a rather complicated and therefore undesirable set of bevel gears which effect pivotable movement of lever members.
U.S. Pat. No. 2,424,524 issued to Watter on July 22, 1947, discloses an adjustable aircraft rudder pedal mechanism. His mechanism has a floor mounted pedestal which swings fore and aft to position the pedals closer to or further away from the pilot as desired. However, the arc of adjustment results in a lowering of the rudder pedal when the mechanism is brought forward from its neutral position. Thus the arc of travel is such that the system does not accommodate the shorter pilot. Also, Watter's device requires floor penetrations in the cockpit.
U.S. Pat. No. 2,610,006 issued to Boyce on Sept. 9, 1952, shows an adjustable rudder pedal control device which can be supported by laterally related slide tracks. This does not provide ergometrically correct adjustments. Further, the linkage connecting the pedals to the rudder mechanism necessitates floor penetrations to reach conventional rudder cables.
Another adjustable rudder pedal mechanism is taught in my U.S. Pat. No. 4,470,570 issued Sept. 11, 1984. That patent discloses an adjustable rudder pedal control mechanism having laterally spaced slide tracks for positioning pedals. The pedals themselves are adjustable in a linear fashion. While that mechanism is an improvement upon earlier devices, it still does not provide an arc of travel matched with the motion of human limbs.
Also, my copending application Ser. No. 120,324 discloses a novel, improved adjustable rudder pedal control assembly. While the mechanism is free of many above-discussed disadvantages of the prior art devices, it is somewhat complex. Also, it requires a floor covering above the major operating mechanism.
In short, in an advanced transport aircraft, it is undesirable to locate rudder pedal control linkages and support mechanisms in the space below the floor in the forward part of the cockpit. Also, the part-by-part fabrication "in place" of the rudder and brake pedal control mechanisms of commonly employed brake and rudder control mechanisms is undesirable. Also, in an age of high aircraft utilization rates, the "in place" servicing of such mechanisms on the part-by-part basis they require is a decided disadvantage. Thus, there is today a need for a modular rudder and brake pedal control device which can be easily and quickly installed below a conventional aircraft instrument panel without penetrating forward bulkheads or pilot station floors and without occupying the limited space available below the forward part of the cockpit. Additionally, it would be desirable to, at the same time, provide a rudder and brake pedal control neutral position adjustment and a pedal normal travel arc which matches the limb length and joint motions of humans pilots.